Pickup trucks are motor vehicles with a rear open top cargo area that is often referred to as a cargo box. Pickup trucks are popular largely because the bed allows the vehicle to be utilized in many different ways, including carrying a variety of types of cargo and towing various types of trailers. Traditionally, the majority of body structures on pickup trucks have been formed from steel alloys. Through years of experience, pickup truck designers have learned how to design steel truck body parts that withstand the variety of demanding pickup truck applications. The current regulatory and economic environment have increased the importance of making pickup trucks more fuel efficient while maintaining or improving functionality and durability. One way to reduce the fuel consumption of a vehicle is to reduce vehicle structure weight.
Aluminum alloys typically have a higher strength to weight ratio than steel alloys. Consequently, replacing steel with aluminum offers the potential for weight reduction. However, the elastic modulus of aluminum is generally lower than elastic modulus of steel. Additionally, fabrication techniques and methods for joining parts that work well for steel parts may not work well for the same aluminum part. Due to these and other differences, simple material substitution does not necessarily produce acceptable design.
Aluminum alloys are generally identified by a four digit number, the first digit of which typically identifies the major alloying element. When describing a series of aluminum alloys based on the majority alloying element, the first number may be followed by three x's or three zeros. For example, the major alloying element in 6xxx (or 6000) series aluminum alloy is magnesium and silicon, while the major alloying element of 5xxx series is magnesium and for 7xxx series is zinc. Additional numbers represented by the letter ‘x’ (or zero) in the series designation define the exact aluminum alloy.